1. Field of the Invention
The subject invention relates to the manufacture of semiconductor devices and, more particularly, to wafer fabrication and/or processing.
2. Description of the Art
The manufacture of semiconductor wafers to create semiconductor integrated circuit devices typically involves a sequence of processing steps that fabricate the multi-layer structure generally associated with the integrated circuit devices. Such processing steps may include (1) the deposition of metals, dielectrics, and semiconductor films, (2) the creation of masks by lithography techniques, (3) the doping of semiconductor layers by diffusion or implantation, (4) the polishing of outer layers (e.g. chemical-mechanical polishing), and (5) the etching of layers for selective or blanket material removal.
Semiconductor integrated circuits are typically fabricated by a layering process in which several layers of material are applied on or in a surface of a wafer, or on a surface of a previous layer. These layers can constitute a metal pattern forming various elements of an electrical circuit. Insulating material and dielectric material are added at various stages of the fabrication process. The layers are typically treated to create a smooth, planar surface. In addition to the surface characteristics, the thickness of the thin film layers can be critical to the performance of a semiconductor and/or its circuit components. For example, the performance characteristics of a particular circuit element may be affected, usually detrimentally, by a dielectric film thickness.
In forming a semiconductor device, one common practice has been to use deposition techniques to apply a particular layer to an existing substrate or layer. In one type of process, a vapor deposition tube sprays a vapor including the layer material onto the workpiece (i.e. semiconductor wafer). In a typical vapor deposition process, the thickness of the thin film layer is measured following completion of the deposition. Under these circumstances, the film thickness is generally controlled by the amount of time that the device is exposed to the vapor deposition process. The subsequent measurement of the film thickness is often accomplished in a xe2x80x9cgo/no-goxe2x80x9d manner in which devices having a film thickness falling outside a predetermined thickness range are rejected and scrapped. In other cases, the semiconductor device is returned for further processing, either for additional material deposition, or for material removal such as in a polishing process. Ordinarily, the economics of mass production mitigate in favor of simply scrapping the component.
Wafer processing such as that described above is typically accomplished in a wafer processing chamber. An exemplary wafer processing chamber has a processing head that introduces a gas or gasses into the processing chamber. A bias voltage may or may not be applied to the processing head. The wafer processing chamber also includes other components for processing the wafer. It is generally necessary to maintain relatively precise control of various parameters such as the temperature of a semiconductor wafer during performance of certain of the processing steps associated with manufacture of the wafer. For example, a number of processing steps associated with wafer fabrication involve complex chemical reactions that require the temperature of the semiconductor wafer to be controlled within predetermined specifications.
In some types of wafer fabrication water is a byproduct of the reaction. Particularly, in wafer fabrication with respect to low k films, water is a major byproduct of the reaction. Additionally, it is desirable to remove as much of the water vapor as the system will allow. The main method for accomplishing water vapor removal is to increase the pumping speeds of the systems vacuum pumps. A problem with this method is that by increasing the pumping speeds to remove unwanted water vapor, other gases needed for processing are removed.
One way to improve the pumping speed is to use a form of Meissner trap. A Meissner trap will freeze the water in the chamber, improving the quality of the film. A Meissner trap will greatly reduce the particle pressure of water vapor in a processing chamber without changing the other gasses being used in the particular process.
The above systems utilize a Meissner or cold trap to improve the ability to pump down (evacuate or reduce the pressure of) the processing chamber. Particularly, the cold trap is used to improve the ability of the processing chamber to pump down quickly to a base pressure needed for wafer processing. A problem with these systems is that they utilize full cryo-pumps that operate at very low temperatures. Another method to remove water vapor is to increase the pump speed and/or pump volume. While increasing the pump speed and/or volume may work to remove more water vapor, such will also remove the beneficial gas or gasses from within the processing chamber. This would then make the system provide more processing gas than necessary.
What is needed in view of the above, is a method of and/or apparatus for removing water vapor from a wafer processing chamber during wafer fabrication.
What is further needed in view of the above is a method of and/or apparatus for removing water vapor from a wafer processing chamber, the water vapor being a byproduct of wafer processing.
What is even further needed in view of the above, is a method of and/or apparatus for substantially continuously removing water vapor from a substantially continuously operating wafer processing chamber, the water vapor being a byproduct of wafer processing.
The subject invention is a process and apparatus for removing water vapor from within a wafer processing chamber, the water vapor generated as a byproduct of wafer processing and/or as a constituent of background gases. Preferably, water vapor removal is accomplished essentially continuously during wafer processing.
In one form, there is provided a method of operating a wafer processing chamber, the wafer processing chamber defining an interior and having a processing head in the interior and in communication with a processing gas, a wafer holder in the interior and adapted to receive a wafer for processing, and a pumping port in communication with the interior and a pump. The method of operating the wafer processing chamber includes the steps of: (a) providing a water vapor accumulator having at least a portion thereof in communication with the interior of the processing chamber; (b) cooling the portion of the water vapor accumulator in communication with the interior of the processing chamber to a water vapor condensation temperature; (c) processing a wafer supported on the wafer holder utilizing the process gas, the wafer processing generating water vapor as a byproduct; and (d) accumulating the generated water vapor on the portion of the water vapor accumulator in communication with the interior of the processing chamber.
In another form, there is provided a method of wafer processing. The method includes the steps of: (a) placing a first surface of a water vapor trap in communication with an interior of the wafer processing chamber; (b) cooling the first surface to a water vapor condensation temperature; (c) processing a wafer in a wafer processing chamber using a processing gas, the wafer processing producing water vapor as a byproduct; (d) accumulating the byproduct water vapor on the first cooled surface; (e) moving the first cooled surface from communication with the interior of the wafer processing chamber to a position exterior to the interior of the wafer processing chamber; (f) moving a second surface of the water vapor trap in communication with the interior of the wafer processing chamber; and (g) cooling the second surface to the water vapor condensation temperature.
In yet another form, there is provided a system for processing a wafer. The system includes a processing chamber, a processing head disposed in the processing chamber and in communication with a source of processing gas, a vacuum port in the processing chamber and in communication with a vacuum source, a wafer holder in the processing chamber and configured to releasably receive a wafer for processing; and a water vapor trap at least partially disposed in the processing chamber. The water vapor trap is operative to cool a first surface of the water vapor trap to a water vapor condensation temperature during wafer processing, to accumulate water vapor generated as a byproduct result of wafer processing utilizing the processing gas and condensed thereon, move the first surface out from the interior, and position a second surface of the water vapor trap into communication with the interior, the water vapor trap further operative to cool the second surface to the water vapor condensation temperature during wafer processing and to accumulate the generated byproduct result of wafer processing.